Research has shown that compared to high frequency alarm tones (on the order of 3 kHz), low frequency alarm tones on the order of a 520 Hz fundamental frequency, square wave can be more effective in awakening children from sleep and can be better heard by people with high frequency hearing deficit which often accompanies advanced age or those exposed to loud sounds for extended periods of time. One of the problems in utilizing such a low frequency (pitch) alarm tone is that it takes significant electrical driving power for a conventional audio output transducer to emit a low frequency alarm tone (for example ˜520 Hz) at sound pressure levels of at least 85 dBA at a distance of 10 feet as required by UL 217 and UL 2034 for smoke and carbon monoxide detectors, respectively as non-limiting examples. This problem is compounded when a low frequency alarm tone is desired to be used in a life safety device such as a conventional, environmental condition detector such as a residential or commercial smoke detector or carbon monoxide detector, as non-limiting examples, since such detector unit components including the sound producing elements are typically contained within a thin vented housing a few inches thick (˜2-3 inches thick in outside dimension) and approximately four to six inches in diameter or approximately square planform. Due to these geometric constraints (largely for a non-intrusive décor and aesthetics), it is difficult to employ a quarter wave resonant cavity comprising a tube with one open end and one closed end. Based on the theory of acoustics, the length of such a resonant cavity (resonator) is one quarter of a wavelength of the fundamental frequency to obtain resonance which reinforces (amplifies) the sound pressure level output of an audio output transducer (for example a speaker, piezo-speaker, or piezoelectric transducer) acoustically coupled to the resonant cavity. For example, for a fundamental frequency of 520 Hz, a quarter-wave closed end, tubular resonant cavity with an open opposite end (Helmholtz resonator) would theoretically need to be approximately 6.5 inches long for air at standard sea level conditions where the speed of sound is approximately 1120 ft/sec. Practically, however, allowing for end effects of the open end of the resonant cavity, the length of such a quarter-wave resonant cavity is on the order of 5-6 inches, still about twice the dimension of the thickness of a conventional, environmental condition detector. Further, in order to achieve the requisite sound pressure level with conventional battery power used in environmental condition detectors (single 9V alkaline battery or 2 to 4 AA or AAA alkaline batteries for example), the audio output transducer must be of sufficient size (typically at least 1-2 inches in diameter) to adequately acoustically couple to the ambient air. Given this transducer size along with a resonant cavity length on the order of 5-6 inches from the example above, it is easily determined that a linear resonant cavity of this size would occupy so much volume inside the housing of a life safety device configured as a conventional environmental condition detector that it would likely cause major blockage issues with the omni-directional inlet airflow qualities desired in smoke and carbon monoxide detectors for maximum environmental condition sensitivity and/or also result in much larger housing dimensions than are conventional for such life safety devices. Therefore, while a resonant cavity is a very useful element to enhance the sound pressure level of an audio output transducer acoustically coupled to the resonant cavity, it is clear that a conventional, linear quarter wave resonant cavity with one open end and one closed end (Helmholtz resonator) is not as geometrically suitable for conventional shape and size environmental condition detectors as a more compact quarter wave resonant cavity is for this application.